This invention relates to a method and apparatus for continuously collecting condensate from a supply of pressurized gas.
When producing a pressurized gas, the prepressurized gas which has a given vapour content is most commonly drawn into a rotary, axial or piston-type of compressor whereby it undergoes pressurization.
During pressurization, the temperature of a given mass of gas invariably increases and is due at least in part to the operating temperature of the compressor through which the gas being compressed must pass. Indeed, it is not uncommon for industrial air compressors of the piston-type variety operating in pressure ranges of 100-150 pounds per square inch (p.s.i.) to generate pressurized gas temperatures in excess of 400.degree. F. In many applications, compressed gas temperatures of this magnitude are viewed as unacceptable and it is therefore quite common to employ one or more aftercoolers downstream of the compressor for lowering the compressed gas temperature.
The aftercoolers may take the form of a simple ambient air heat exchanger or a water-jacketed heat exchanger. Although the temperature of the pressurized gas is reduced, these heat exchangers are not intended nor are they capable of functioning as vapour condensor collectors since whatever condensation is produced in the aftercooler it is normally swept along with the throughput of the pressurized gas. Condensate which is formed is usually collected and drawn off from the stream of pressurized gas by means of a cyclone separator or other forms of condensate collectors specifically designed for that purpose.
When a confined stream of pressurized gas is permitted to cool along the length of its confining conduit, due to the conduit's own heat-exchange exposure to a cooling fluid such as water or ambient air, for example, the vapour in the compressed gas stream condenses therealong downstream of a point where the dew point of the compressed gas at a given temperature is in equilibrium with a given temperature of the cooling fluid. In the case of compressed air, where air driven tools are employed, this can result in the passage of water as condensate through the tool and cause premature wear in the tool resulting from a washing away of its lubricant. In extreme cases, the condensed water vapour may freeze as a result of its confining conduit being exposed to temperatures below 32.degree. F.
There has been a need, therefore, to devise an apparatus and method for continuously collecting condensate from a supply of compressed gas which, using the cold temperature approach, is capable of collecting and withdrawing condensate where the temperature dew point of the vapour in the compressed gas is greater than the temperature of the cooling fluid in a simple and inexpensive manner.
For example, large quantities of compressed air have been traditionally used, in combination with water under pressure, to produce what is described as "man made" snow. Commonly, a aftercooler and cyclone separator as above described is employed. However, downstream of the separator, it is not uncommon for the stream of pressurized air to undergo further cooling with the result that additional water vapour is condensed. This condensate hopefully is discharged at the snowmaking nozzle but where it undergoes freezing, if sufficient quantities are built up, it can clog one or both of the supply conduits to the snowmaking gun or the snowmaking gun itself.
Since most on-slope compressed air supply conduits for making man-made snow are buried underground, the ground temperature about the conduit can generally be taken as being, at its lowest, slightly above the freezing point (0.degree. C.). The actual production of man made snow, however, is normally only undertaken where the ambient air temperature is 0.degree. C. or less and quite often, significantly less than 0.degree. C. Ideally, therefore, in snowmaking operations, water condensate should be extracted from the pressurized air at a dew point temperature which is below the ground temperature so that as the pressurized air proceeds along the supply conduit, it does so at a temperature somewhat above the dew point temperature at which its water vapour will condense and collect. Optimally, the dew point temperature of the pressurized air used in such applications should be less than the existing ambient air temperature.